II.ii. The Fishmonger Scene - BBC '80

Jacobi's Hamlet walks in on Polonius and the Royals, reading and feigning madness. This is very different staging from the usual scurrying away, allowing Hamlet to interact with his parents in this "state". He makes a show of being repulsed by and afraid of his mother, but his furtive looks provide proof that this is an act. His puts a lot into his gestures, for example actively seeing things he mentions as metaphor, pointing to God and to carrion (carrion that shockingly makes him think of asking about Ophelia). This is a character trait he picks up from other places in the play, such as when he makes Polonius look at clouds.

But of course, it's in his interpretation of the words that Jacobi shines most. He gives every line its own nuance. For example, his "God have mercy", usually an annex to his "Well" (i.e. thank the Lord that yes, I am well) becomes a show of exasperation with Polonius. His "Words, words, words" starts out as a strange realization that he is reading words, followed by disgust that that's all they are. Jacobi turns the line into a precursor for Hamlet's distress when he must "unpack his heart with words". For Hamlet, while words are his greatest gift and weapon, they are not enough to express his being - a central irony of the character. Hamlet actively dislikes being bound by his author's words, which is why we often talk about him getting away from Shakespeare.

From moment to moment, Hamlet's attitude may change. At "between who", he becomes conspiratorial, a parody of Polonius' obsession with hyper-surveillance. At "into my grave", where other actors have made the line sarcastic, Jacobi makes his Hamlet feign great fear and anguish, as if he were both misunderstanding Polonius and taking him at his word. He lets out little laughs, lascivious ooohs, and injects comic pauses (for example, when reading the "slanders", as if to confirm the words using Polonius as a template).

"Except my life" becomes a full-blown suicide attempt (again, for show), putting his dagger to his stomach and threatening to push it in.
Polonius' reaction is to quickly walk away, afraid perhaps of being accused of murdering Hamlet, or of pushing him into suicide. As soon as he runs, Hamlet stops this pretense, but it is a dark, cruel joke he revisits more seriously in the "To be or not to be" speech.